Particle-matrix composite materials may be composed of particles embedded in a matrix. For example, relatively hard particles of a carbide ceramic such as tungsten carbide (WC) or titanium carbide (TiC) may be embedded in a matrix of a metal such as cobalt (Co), nickel (Ni), or alloys thereof. These particle-matrix composite materials are used frequently for cutting tools due to improved material properties of the composite as compared to the properties of the particle material or the matrix material individually. For example, in the context of machine tool cutters, refractory carbide ceramic provides a relatively hard cutting surface but is relatively brittle and may not be able to withstand cutting stresses alone, whereas a metal may be too soft to provide a good cutting surface. However, inclusion of the refractory carbide ceramic particles in a more ductile metal matrix may isolate the hard carbide particles from one another and reduce particle-to-particle crack propagation. The resulting particle-matrix composite material may provide a relatively hard cutting surface and improved toughness.
Although particle-matrix composite materials have many favorable material properties, one difficulty in the use of particle-matrix composite materials is that welding using localized heat, such as arc welding, may cause cracks to occur in particle-matrix composite materials.
For example, U.S. Pat. No. 4,306,139 to Shinozaki et al. describes a method for welding a material comprising tungsten carbide and a nickel and/or cobalt binder to an iron base member. Shinozaki et al. discloses that chromium has a strong tendency to combine readily with carbon and will react with the carbon in the tungsten carbide to form carbides of chromium. As a result, the tungsten carbide is decarburized to (W.Ni)6C or (W.Co)6C, which very frequently appears at the boundary of the material and the weld. These carbides are a few times greater in particle size than tungsten carbide and are very brittle, and can thus cause separation of the weld and cracking. To avoid this problem a nickel-alloy filler material containing no chromium (Cr) and at least 40% nickel by weight is applied with a shielded arc welder or tungsten inert gas welder.
It has been observed however, that welding particle-matrix composite materials (for example, a material comprising tungsten carbide particles in a cobalt matrix) to steel according to Shinozaki et al. may still result in cracking of the particle-matrix composite material proximate the weld.
In view of the above, it would be advantageous to provide methods and associated systems that would enable the welding of a particle-matrix composite material without significant cracking. Additionally, it would be advantageous to provide methods and associated systems that would enable the welding of a particle-matrix composite body to another body using welding techniques involving a focused heat source, such as an electric arc or a laser, without significant cracking resulting in the particle-matrix composite body.